The present invention relates to a fiber lubricant composition which is particularly useful for lubricating a spunbonded nonwoven fabric and to fibers and fabrics having said lubricant composition thereon.
More specifically the fiber lubricant composition of this invention consists essentially of a synergistic mixture of certain silicone-glycol copolymers and butyl stearate which, when applied to spunbonded nonwoven polypropylene carpet backing, provides unexpectedly good lubrication for needle-tufting of the backing and an unexpectedly low flammability of a tufted carpet produced therefrom.
A spunbonded fabric is a continuous filament nonwoven fabric made by combining all the steps from polymer preparation to finished fabric in one process. Curtains of polymer filaments are extruded, drawn, forwarded to a belt and combined there into a web with the required design. The web is then bonded and can be finished in the same single process.
The basic process steps for making spunbonded nonwoven fabrics are quite simple. Multiple spinnerettes extrude large numbers of polymer filaments which are drawn and oriented in groups, by rolls or by high velocity air, and then projected, in some desired geometrical array, as a web onto a slowly moving porous belt provided with suction to hold the web. The belt then carries the web to a bonding operation such as binder application and/or heater rolling and then to one or more further operational steps in the process. These latter steps can be the traditional textile finishing steps such as printing or embossing when process speeds are compatible.
There are many spunbonded nonwoven fabrics available commercially. Examples of such materials are those based on synthetic fibers, such as polyesters, polyamides and polyolefins, such as polypropylene, polyethylene, or combinations of the foregoing. The particular fiber type used will depend on the nature of the finished product one wishes to make. Each uses for spunbonded nonwoven fabrics ranges from such things as book covers, to clothing fabric to carpet backing.
One of the most significant commercial uses of spunbonded nonwoven fabric is the use of spunbonded nonwoven polypropylene as a carpet backing. The spunbonded nonwoven polypropylene fabric has been substituted for the woven jute backing materials that have been used heretofore in the production of carpets.
In this use the carpet yarn is threaded through a suitably large needle which is then punched through the spunbonded nonwoven polypropylene fabric, designated as the primary backing. A looper device catches the yarn on the opposite side of the backing to form loops or tufts and the yarn and needle are then withdrawn to complete the formation of the loop or tuft. The backing fabric is then advanced and the cycle is repeated to form additional tufts. The tufts make up the pile or face of the final carpet. A commercial tufting machine may have up to 2400 needles in a row all working in unison to make a carpet up to 15 feet in width.
The primary backing, which is the spunbonded nonwoven polypropylene fabric, is the structural base of the carpet. It holds the tufts in place and provides dimensional stability and strength to the carpet. To the back of the tufted spunbonded nonwoven polypropylene backing there is applied a glue, for example a latex of natural rubber or styrene-butadiene rubber, which coating firmly anchors the tufts in place and keeps them from pulling out. A jute or foam back may then be placed on the glued carpet backing to act as a pad or cushion.
In the development of this use of the spunbonded nonwoven fabric it was found that the needles did extensive damage to the carpet backing on penetration of the structure, resulting in a large loss in strength during the tufting process.
Campbell, et al., U.S. Pat. No. 3,867,188 discovered that when certain silicone-glycol copolymers were applied to the spunbonded nonwoven polypropylene backing the penetration of the needle therethrough in the tufting process was facilitated and the backing damage and its attendant loss of strength could be significantly reduced.
Useful as Campbell et al's discovery is, it suffers from a drawback common to previous processes comprising using a silicone as a lubricant for spunbonded nonwoven carpet backing, i.e. increased flammability of certain carpeting produced therefrom. It appears that as the carpet yarn is punched through a carpet backing that has been lubricated with a silicone-containing composition it picks up some of the lubricant composition, thereby resulting in a carpet having the lubricant composition on its facing as well as on its backing. It is thought that, at certain levels of add-on, silicone compositions are responsible for the enhanced flammability of some thermoplastic yarn materials, that is demonstrated in some testing procedures.